Forward error correction (also referred to herein as FEC or error correction) has been incorporated into many digital communication systems. For example, FEC is specified in the IEEE 802.11e draft. In conventional practice, the Media Access Control (MAC) layer can selectively apply FEC to the Physical Layer Service Data Unit (PSDU). The PSDU includes the MAC header and the MAC payload. FIG. 1 diagrammatically illustrates pertinent portions of a conventional 802.11 communication apparatus that includes FEC capability. In the example of FIG. 1, a selector 13 in the MAC layer has an input 14 which receives the data stream 11 that passes from the physical (PHY) layer to the MAC layer. For each PSDU in the data stream 11, the selector 13 determines whether to send the PSDU to a data path 17 for regular MAC processing or to a data path 19 for MAC processing with FEC.
The decision of the selector 13 is determined by its control input 12, which is driven by the output of an FEC decision decoder 15. The FEC decision decoder 15 determines whether to use regular MAC processing or FEC MAC processing based on the value of a predetermined bit in the MAC header. Such use of a single bit to control the selection decision at 13 limits the accuracy of the decision at 13 to the bit error rate (BER) of the system, for example, a BER of 10−4 for IEEE 802.11 systems. Even if FEC has been applied to a given packet, the FEC decision decoder 15 cannot take advantage of the improved BER provided by the FEC, and the accuracy of the decision at 13 remains limited to the nominal BER of the system, for example, the aforementioned BER of 10−4 associated with IEEE 802.11 systems.
It is therefore desirable to improve the accuracy of MAC-level FEC decisions such as illustrated generally at 12-15 in FIG. 1, and to provide a more robust indication of the use (or non-use) of FEC.
Various embodiments of the invention improve the accuracy of the receive-side FEC decision and the robustness of the FEC indication by: making the FEC decision based on the results of FEC decoding applied to the MAC header; providing an FEC indication bit in the PHY component of the packet; and using a plurality of bits to encode the FEC indication in either the PHY component of the packet or the MAC component of the packet.